This invention relates to blends comprising certain polyamides and polyarylene sulfides. More particularly, the invention relates to a method for improving the processability of a polyterephthalamide which, when filled with glass fibers, has a heat deflection temperature at 264 psi, according to ASTM D-648, above about 240.degree. C., and to the corresponding filled polyphthalamides containing fibrous or particulate fillers, preferably glass fibers, by blending therewith an amount of a polyarylene sulfide sufficient to reduce the melt viscosity.
Polyphthalamide compositions which, when filled with glass fibers and molded, have heat deflection temperatures at 264 psi, determined according to ASTM D-648, above about 240.degree. C. are disclosed in the art. Among such polyphthalamides are polymers comprising recurring terephthalamide units, preferably in combination with one or more other carboxylamide units, for example, adipamide or isophthalamide units. Compositions comprising such polyphthalamides, including particulate-filled and fiber-filled compositions, exhibit desirable thermal properties including high deflection temperature as well as high tensile strength and flexural modulus and are useful in various applications including preparation of molded articles, fibers, and laminates. Such compositions have utility in various applications, the neat and fiber-filled compositions being particularly suited for extrusion and molding applications.
Although these polyphthalamides have found wide acceptability for a great variety of end uses, the resins are somewhat difficult to process thermally. The art continues to seek more readily-processed materials exhibiting still further improvement in such characteristics as solvent resistance and resistance to thermal-oxidative degradation, sometimes also referred to as thermal endurance. Such improvements would lead not only to longer useful life of products where demanding environments are encountered such as in under-the-hood automotive parts, but also utility in additional applications with even more stringent requirements.
In general, it is known that modification of polymer properties may be achieved in various ways. Modification of the molecular structure of a given composition through the use of additional monomers in polymerization can lead to desirable improvements in some properties. However, the same often are accompanied by loss of other desirable properties and use of additional monomers is not always practical due to process considerations. Addition of other materials to a polymeric composition may lead to property improvements without complicating a polymerization process; however the effects of additives often are unpredictable and, again, improvements in some properties often are achieved at the expense of other properties. For example, addition of high strength fibers such as glass or graphite fibers to polyamides is known to improve mechanical properties, such as tensile strength and flexural strengths and moduli, but these improvements are achieved at the expense of ductility. Blending a given polymer with one or more other polymers may give blends with a combination of properties intermediate of those of the individual components; however, processing requirements often limit the number of candidates that can be blended with a given polymer in an attempt to attain desirable property modifications and properties of a blend may or may not reflect those of its components depending on compatibility of the components with each other, reactivity thereof under blending or processing conditions and other factors.
Polyarylene sulfides are well known thermoplastics that find use in molding applications. As reported in "Technical Information On Ryton.RTM. Polyphenylene Sulfide Resins And Compounds" published by Phillips Petroleum Company, Plastics Technical Center, commercial polyphenylene sulfides designated Ryton polyphenylene sulfide exhibit excellent dimensional stability, inherent flame retardancy, thermal stability, chemical resistance, desirable electrical properties and ease of processing.
Blends of certain polyamides with polyarylene sulfides for various purposes to obtain blends having modified properties relative to those of the neat resin(s) are disclosed in the art. Blends containing from 0.01 to 10 wt % polyarylene sulfides with semicrystalline polyamides such as nylon 6 and polyamides obtained by condensation of a dibasic acid such as adipic, sebacic or terephthalic acid and a diamine such as hexamethylene diamine or 1,12-dodecanediamine that have improved molding characteristics and reduced warpage of parts molded therefrom are disclosed in U.S. Pat. No. 4,292,416. According to the patentee, the polyarylene sulfide useful in these blends must have a higher melting point than that of the polyamide. Inclusion of conventional additives for polyarylene sulfides, such as lubricants, stabilizers, pigments, dyes, fillers and plasticizers, also is disclosed. The patentee speculates that the improved properties of the blends result from a nucleating effect on the polyamide component imparted by the polyarylene sulfide component whereby crystallinity of the polyamide increases and properties dependent on degree of crystallinity are enhanced. The patentee also discloses that nucleation of polyamides can be accomplished through use of other such higher melting polymers which, during cooling, solidify prior to the polyamides so as to provide sites for nucleation.
U.S. Pat. No. 4,528,335, also assigned to Phillips Petroleum Company, discloses blends of amorphous polyamides, i.e., those having less than about 20 percent crystallinity, with polyarylene sulfides melting at about 260.degree. to about 400.degree. C. at weight ratios of 0.1:100 to about 100:100 are disclosed in U.S. Pat. No. 4,528,335. The blends, described to have improved impact strength and reduced shrinkage and warpage, may also contain fillers such as glass and carbon fibers.
Blends of low viscosity, uncrosslinked polyarylene sulfides not suited for injection molding, an epoxy compound and, optionally, a thermoplastic resin having a viscosity of at least 1,000 poise are disclosed in U.S. Pat. No. 4,528,346. According to the patentee such blends exhibit improved melt stability relative to commercially available injection molding grade polyarylene sulfides. Included among the various thermoplastic resins disclosed to be suitable as the optional component are polyamides. Adding fibers and inorganic fillers to such blends is also described.
Published Japanese Patent Application No. 55-135160 discloses blends of polyphenylene sulfide with nylon, unsaturated polyester or polyphenylene oxide resins, such resins being used to increase fluidity of the polyphenylene sulfide without sacrifices in other properties. Blends with nylon 6 and nylon 66 are specifically disclosed as are blends that contain glass fibers.
International Patent Application No PCT/US82/01688 (International Publication No. WO 83/02121 ), discloses adding a small amount of polyacrylamide or polyamide to a polyarylene sulfide melting from about 260.degree. to about 400.degree. C. to obtain compositions that are less corrosive to metals than neat polyphenylene sulfide. Among the disclosed polyamides are nylon 4, nylon 6, nylon 66, nylon 9, nylon 10, nylon 11, nylon 12, nylon 610, nylon 6T (polyhexamethylene terephthalamide), poly(p-phenylene terephthalamide), poly(m-phenylene isophthalamide), poly(N-N-diphenyl-p-phenylene isophthalamide), and polyamides derived from bis(p-aminocyclohexyl)methane and a dicarboxylic acid such as dodecanedioic acid. In the examples, blends containing up to 1 weight percent polyamide are disclosed.
International Patent Application No. PCT/NL85/00046 (International Publication No. WO 86/03212), discloses blends containing 5 to 50 weight percent polyarylene sulfide and 95 to 50 weight percent polytetramethylene adipamide. Use of mixtures of polytetramethylene adipamide with other polyamides in such blends also is disclosed as are blends containing fibers and particulate fillers.
U.S. Pat. Nos. 3,354,129, 3,862,095 and 3,790,536 disclose arylene sulfide polymers and processes for preparing them. These patents mention that such polymers can be blended with various materials including other polymers.
While the patents and publications discussed above disclose various blends, they do not disclose blends of a polyphthalamide component and a polyarylene sulfide component wherein the polyphthalamide component comprises terephthalamide units and which, when filled with 33 weight percent glass fibers, has a heat deflection temperature at 264 psi, according to ASTM D-648, above about 240.degree. C. Further, the art does not disclose or suggest that blends of such a polyphthalamide component and a polyarylene sulfide component would exhibit the properties achieved according to this invention.
The art also does not disclose or suggest blends according to the invention comprising a polyphthalamide of fast or intermediate crystallization rate, as indicated by heat deflection temperature at 264 psi according to ASTM D-648 above about 240.degree. C. when filled with 33 weight percent glass fibers, and a polyarylene sulfide component. Further, contrary to the teachings or express requirements of the art, it is not a requirement that the polyarylene sulfide melting point exceed polyamide melting point in the practice of the invention, and the melting points of some polyphthalamides found suitable for use in blends according to this invention exceed those of the polyarylene sulfide component by at least about 15.degree. C.
It is an object of this invention to provide blends of a polyphthalamide component comprising terephthalamide units and, optionally, isophthalamide units and adipamide units which, when filled with 33 weight percent glass fibers, has a heat deflection temperature at 264 psi, according to ASTM D-648, above about 240.degree. C. and a polyarylene sulfide component, as well as filled compositions based thereon having utility in molding and other applications. A further object of the invention is to provide such blends with improved processability in which properties such as water absorption, methanol resistance, thermal endurance or flame resistance are improved relative to those of the polyphthalamide component. Other objects of the invention will be apparent to persons skilled in the art from the following.